Fractional distillation of metals.



Y c. G. PINK. FRACTIONAL DISTILLATION OP METALS.

y APPLICATION FILED FEB.7, 1908.

996,474, Patented June 27, 1911.

To Fum w C? Q J s S f Q Witnesses: Inventor COLIN Gr. FINK, SCHENECTADY,NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION 0F NEWYORK.

Specification of Letters Patent.

FRACTIONAL DISTILLATION OF METALS.

Patented June 27, 1911.

Application led February 7, 1908. Serial No. 414,683.

To all whom 'it may concern:

Be it known that I, COLIN` G, FINK, a citizen of the United` States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Fractional Distillationof Metals, of which the following is a specification.

This invention comprises certain improvements in the treatment of or soas to effect a reduction of the ore and a purification of the product inone continuous operation.

My procedure is applicable to a variety of ores, but in general to oreswhich contain volatilizable substances, for example, as antimony andarsenic. The metallurgical treatment of ores of this kind is at presentaccomplished by a long and expensive process. By taking advantage of thelowered temperature of vaporization of substances in a vacuum not onlyare the methods of treatment simplified, but a better yield and purerproduct is obtained. Furthermore, low grade ores may be used whichformerly could not be worked to advantage.

The novel features of my invention are l pointed out in the appendedclaims.

A detailed description of procedure with' certain ores will be given toillustrate the general nature of my invention.

The accompanying drawing shows a resistance furnace, together with meansfor operating the furnace continuously and maintaining a vacuum in thesame.

As an illustration of my invention the treatment of stibnite, an ore ofantimony,

may be described. This is a sulfid lof antimony having the chemicalformula Sb2S3. It is a soft grayish mineral with a metallic luster. Therecovery of antimony from stibnite is at present accomplishedI by aseries of separate steps, such as concentration, volatilization,oxidation and reduction.

A temperature of 1500-1700O C. is necessary to vaporize antimony atatmospheric pressure. It is because of this high temperature that adistillation of the metal from the slag after reduction of the metal isnot feasible. The output is impure and the loss of metal is considerableunder atmospheric pressure. However, `at a pressure of 5 6 m. In. ofmercury, antimony vaporizes at 7 35 C. This very much lower temperaturemakes it possible to combine with the process of reduction a Iprocess ofdistillation, which combination results. in an almost quantitative yieldand a purer product.4 I mention` this fact to show how greatly thetemperature of distillation is lowered by' a high degree of evacuation.Practically, l

vhave not found it necessary to attain this high degree of evacuation inorder to carry out my process. At a pressure of about 40 m. m. ofmercury, the antimony will be readily distilled at a temperature in theneighborhood of 1200-13000 C. As no precise degree of evacuation need beattained no more exact temperatures need be given.

As is evident, lall loss of metal due to burning or oxidation isavoided. Another advantage -of the vacuum process is the greater speedof the reaction, due to the fact that the gaseous products are quicklyremoved during the reduction.

According to one mode of carrying out my invention with stibnite usingan ore con tainingV 62% of antimony, 11.3 parts of stibnite, 12 parts oflimestone, 2J, parts of coke vand 6 parts yof uorspar are ground untilthe resulting powder will pass through a 20 meshsieve,--and the mass isintimately mixed and then treated in the furnace as hereafter described.The calcium of the limestone serves to combine with the sulfur of t-heore. The carbon dioxid gas liberated from the. limestone is reduced t-othe monoxid by the carbon of the charge and of the electrodes. Thecarbon dioxid and monoxid gases ,serve to make the charge porous andassist mechanically in the extraction and distillation of the reducedantimony. It is possible that the carbon monoxid likewise furthers-the'reduction process. The carbon also serves the purpose of increasing theconductivity of the charge, so as to enable a current to. be passedthrough the charge in order to heat the same. The fluorspar seems tofacilitate the separation ofthe antimony from the slag during thedistillation which is later described.

The powdered mixture of ore is placed in a furnace such as sho-wn in thedrawing. The furnace walls 1 are made of metal, such as iron. Thefurnace is lined with a refractory material such as tire brick. Caremust,be taken to make all the joints and parts of the furnace air-tight.The furnace is provided with interchangeable water-cooled condensingchambers 3 and 4,

communicating with the furnace by means of a conduit 5. An exhaust pumpcommunicates with the charging chambers by tubes 6 and 7. As thecondensing chambers communicate with the furnace, the pump will exhaustthe furnace as Well as the chambers. By closing cock 8 condensingchamber 3 is cut out, by closing cock 9 condensing chamber 4 is cut out.Either chamber may thus be cut out in order to removepits contents, theantimony being in the meantime received in the other chamber. Chargingchamber 10 permits ore to be introduced into the chamber withoutinterrupting its operation, as Will be further eX- plained. Electrodes11 and 12 pierce the furnace Wall through air-tight., watercooledpackings 13 and 14. Tlecharge is placed within the chamber 15 in contactwith electrodes 11 and 12, and a current is passed through the charge.Valves 9 and 16 are closed and Valve 8 is opened. Condensing chamber 3is thus put linto communication with the furnace. The valve 17 to thepump is closed, and the valve 18 to the pump is opened. The pump is putinto operation. The heating is performed in two stages. The temperatureis gradually raised to 600-700o C. and maintained at that point for oneand a half hours, the pump being in constant operation. According to mypresent belief the following action takes place:

The fact that calcium sulfid, CaS, is formed in the slag, and C() gas isgiven 0H during the operation makes it reasonable to suppose that thisreaction takes place. The constant operation of the pump will maintain avacuum of about 40 1n. m. in the furnace. The current is now slowlyincreased until a temperature/of about 13000 is obtained and continuedat this point for about one hour, the vacuum'pump operatingcontinuously. During this stage of4 process the antimony is distilledfrom the mixture into the chamber 3. The chamber 3, being Water-cooled,serves as a condensing chamber, the antimony assuming the solid state. Afresh charge of ore is meanl While fed into the chamber 10, through thevalve 19, through a funnel or other means,

the valve 16 leading to the furnace remaining closed. The outer valve 19is now closed, and the valve 16 opened.

The charge drops through the chute 20 into Vthe furnace. The operationof the pump is interrupted by closing cocks 8 and 18 for a short time,or until the gases liberated by the charge have accumulated (indicatedby the pressure gage) to an `extent `sufficient to allow the slag to beremoved.

A pressure of three-fourths of an atmosphere inside the furnace will besuflicient. During this interval no antimony is volatilized. Theimpoverished charge can be removed by lowering the hinged bottom 21after the furnace has partly cooled and filled with air. The pump isthen again set into operation, cock 18 is opened', and after a shorttime cock 8, until the desired degree of evacuation is restored by thepump. By this means the operat-ion of the furnace is continuous. As theslag need not be removed after each fresh charging, the vacuum may becontinuously maintained for a long time. The charging chamber 10 isconnected to the pump through the tube 23. If necessary chamber 10 isevacuated before opening the valve 16 so as not to impair the vacuum'inthe furnace when introducing a fresh charge.

The distilled antimony is removed from the chamber 3 when a sufficientamount has accumulated, the chamber 3 being cut out by closing cocks 8and 18. Chamber 4 is cut in by opening cocks 9 and 17 and serves toreceive the distilled ore. Air is admitted into the .condensing chamberbefore emptying the same by means of cock 22', in order to destroy thevacuum. The chamber 3 may then be opened and the charge removed. Chamber4 is similarly provided with a cock 24. The slag consists mainly ofcalcium suld with less than 1% of antimony. The reduced antimony is 99%ure.

The reduction of the stibnite may also b accomplished by heating thepowdered ore with finely divided metallic iron. Two parts by weight ofstibnite are mixed with one of iron. The temperature of the charge israised 7 00 for 20 minutes. During thisy time reduction takes place withthe .formation of iron suld and metallic antimony. lt is myopinionthatthe following reaction takes place;

sbgsmyarezsres/Jrasb.

The temperature isthen` carried to 12001 metallic antimony is wellcrystallized. The crystals are of a very bright luster. The slag is afine granular mass of iron sulid.

l Instead of metallic iro'n, an oxid ore such as hematite, limonite,magnetite, and so forth may be used7 the oxygen of the hematite servingpartly to unite with the sulfur of the stibnite to form sulfur dioxidSO2, and the remaining sulfur combining with the reduced iron to formsulfid of iron. This sulfur dioxid is a valuable by-product. From 2 to 3parts by weight of powdered carbon to one part of ore is added to thecharge. This addition increases the conductivity of the charge, and byforming carbon monoxid keeps the charge porous and assists in thedistillation of the antimony.

Instead of an iron ore, a chrome iron ore, Ias for example, chromite canbe used. Chromite is a brittle, iron-black mineral of the chemicalcomposition expressed by the formula FeOCr2O3. For-example, about fourparts of finely ground stibnite are mixed with two parts of finelyground chrome iron ore. One part by weight of powdered coke or charcoalis added for the same purposes as set forth above in-connection with theiron ore. The powdered mass should be line enough to pass through a 20mesh sieve. The mixture is heated in two stages. It is first heated at900 effect the reduction of the antimony, iron and chromium. Partof theantimony is volatilized at this temperature. It is my belief that thereduction takes place essentially according to one or both of thefollowing equations:

But I do not wish to be limited by this view. The temperature is nowraised to about 15000 for one to two hours in order to volatilize outthe remainingreduced antimony. A very pure product and a practicallyquantitative yieldare obtained. The product. in the lower part of thefurnace is chrome-iron and slag. Removal of the slag and reduced metaland re-charging of'the furnace may be accomplished in the same.

for one to two hours tol of'antimony, the yield In the case of some oresthe addition of a reducing agent is 'not necessarv. The heat treatmentalone may be sufiicient .to bring about a separation or dissociationofthe elements, and has thus the same effect as areduction. ElementsVother than antimony may thus be recovered. Both of these features areillustrated by the following example. Smaltite, a cobalt arsenid, CoAs2may be reduced by this process. The ore usually contains a certainamount of sulfur and iron, and the cobalt is often replaced tosome'extent by nickel. Smaltite is a tinwhite, brittle mineral. Bysubjecting this ore to a` distillation process both metallic arsenic andan alloy of cobalt iron and nickel may be produced.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. The process of reducing the sulfid compound of a volatilizable metalwhich consists in mixing said compound with a reaction material whichwill combine lwith the sulfur at an elevated temperature to form arelatively stable compound, heating said mixture to the reactiontemperature and then removin the reduced metal from the by-products 0%the reaction by distillation in an attenuated atmosphere.

2. The process which consists in mixing antimony ores with a reactionmaterial yielding reducing ases and a basic compound having an a nityfor the non-metallic constituent of the ore and distilling oit the,antimony at an elevated temperature and at a reduced pressure.

3. The process which consists in heating a mixture of suli'd ofantimony,lime and carbon and removing the gaseous reaction products anddistilling the reduced antimony in an attenuated temperature.

4. The process which consists in heating a mixtureA of sullidofantimony, lime and Acarbon to a temperature of about 600 to 700 C.,removin the gaseous reaction products and distilling the reducedantimony at a temperature of about 1300o C. in an attenuated atmosphere.

5. The process which consists in reducing an antimony compound in thepresence of reaction material forming a slag with a.

Vnon-metallic compound of said compound.

which is more refractory than antimony and volatilizing and conductingaway the reduced antimony from the slag, all in a highly attenuatedatmosphere.

G. The process which consists in heating a reaction mixture containing aIvolatilizable metal to the reduction temperature in a sub- I vacuumover the reaction mss, and finally stantiai vacuum, and maintaining saidtemdistilling the reduced antimony at a higher perature to complete thereduction, then intemperature in said vacuum.

creasing the temperature to the volatilizing In Witness whereof, I havehereunto set 5 point of said metal and conducting away my hand this 5thday of Feb., 1908.

and condensing the reduced metal. v 7. The proozegss Which consists inheating COLIN G FINK' antimony sulfid in`the presence of a reduc-Witnesses:

ing agent at a temperature of about 600 to 1 HELEN ORFo-RD,

10 700O C. While maintaining asubstantial i BENJAMIN B. HULL.

